What does undetectable = untransmittable (U=U) mean?

When a person is living with HIV and is on effective treatment, it lowers the level of HIV (the viral load) in the blood. When the levels are low (below 200 copies/ml of blood measured) it is referred to as an undetectable viral load. This is also medically known as virally suppressed. At this stage, HIV cannot be passed on sexually.

This scientific evidence was gathered from several studies. The studies included thousands of heterosexual and gay couples in which one partner had HIV and the other did not. Over the course of the studies, they found that there was not a single HIV transmission from an HIV-positive partner who had an undetectable viral load.

When a person is undetectable, condoms are not required to prevent HIV transmission, but being undetectable does not protect against other sexually transmitted infections.

U=U applies to transmission through sex only. We have more information about the risk of transmission through other routes, including breastfeeding and sharing needles.

We have provided a U=U page specifically for HIV-negative people. As well as U=U, PrEP is another way to prevent HIV transmission, for HIV-negative people who may not know the HIV status of their sexual partner(s) or whose sexual partner(s) is not undetectable.

About us

NAM is a charity based in the United Kingdom. We work to change lives by sharing information about HIV & AIDS. We believe independent, clear and accurate information is vital in the fight against HIV & AIDS.

Our information is intended to support, rather than replace, consultation with a healthcare professional. Talk to your doctor or another member of your healthcare team for advice tailored to your situation.